Cereal crop biomass and fiber from agricultural processing operations include materials such as hulls, distillers' dried grains, and spent germ, as well as other postharvest debris. Historically, these materials typically have been used for ruminant fodder. The substantial value as well as quantity of biomass resources lost as ruminant fodder has become more apparent with the arrival of biofuels, particularly ethanol. Additionally, the biomass resources have been recognized to have potential value as a source of food ingredients, including nutritional and fiber products.
The technologies needed to convert biomass to biofuel have been the subject of study for at least three decades. Conventionally, the conversion of biomass fiber to ethanol is a multistep process. This process typically begins with the identification and collection of a suitable fiber material. A common feature of conventional process schemes is the hydrolysis of the biomass to produce a heterogeneous broth of fermentable carbohydrates and an array of biomolecules. This broth is subsequently fermented using a select microorganism to produce ethanol. The fermented broth then is distilled to recover the ethanol. The extracted broth typically is then concentrated, dried, and used in various applications, such as animal feed.
The biofuel industry has largely focused on simple readily available grain biopolymers, such as cereal starches. While starches will continue to be used, the realization that only a finite quantity of these can be diverted to the production of biofuels has resulted in a need for the identification and development of other feedstocks, particularly feedstocks that can be processed in economically viable methods.
Efforts have been made to develop new feedstocks and methods, but, in many instances, technologies developed in the laboratory are either cost prohibitive, challenging to scale up, or not robust enough to accommodate industrial practices and needs. In many instances, conventional processes can yield by-products that are detrimental to downstream processing steps.